The present invention relates to a hand type electric message machine, and more specifically to a massage machine in which a head is flexibly coupled to a hand case and is vibrated so as to provide massage effect, and an improvement made in the mounting structure of an unbalance weight installed to vibrate the head. More specifically, the the unbalance weight is installed so that the center of gravity of a weight element is positioned on a line extending radially from a bearing in a vibration head member.
In a conventional head type massage machine, a head is flexibly coupled to a hand case and an unbalance weight contained in the head is rotated and thus, the head is vibrated, and a massage effect is obtained through the vibration of the head. A conventional method for mounting an unbalance weight on a head is that a longitudinal pair of bearings are installed within the head, a motor is contained in a hand case and a top end portion of a rotary shaft coupled through a transmission spring with an output shaft of the motor is supported by both bearings, and the unbalance weight is mounted on the top end portion of the rotary shaft at position between both bearings. In this method, however, work to make the center of both bearings coincident during the assembling is quite troublesome, and if the center is not coincident the bearing portion will be subjected to heat, seizure, partial abrasion, noise or the like. In order to improve the above-mentioned situation, a mounting structure of an unbalance weight has been proposed by the present applicant (Japanese utility model application laid-open No. 18453/1985). That is, as shown in FIGS. 9 and 10, a motor M is contained in a hand case 1 and a top end portion of a rotary shaft 10 extending from the motor M through a transmission spring 5 is supported by a single bearing 8 in a head 2, and an unbalance weight 9 comprising a base portion 9a and a weight element 9b formed on a part of a periphery of the base portion 9a is mounted on the top end portion of the rotary shaft 10 so that the center of gravity of the weight element 9b is positioned on a line extending radially of the bearing 8, and the unbalance weight 9 is rotated. In this mounting structure of the unbalance weight, a problem resulting from heat is not produced and the assembling work is simple.
In the above-mentioned mounting structure of the unbalance weight in the prior art, since the unbalance weight comprising the base portion (disc portion) and the weight element formed on a part of the periphery of the base portion is mounted on the top end portion of the rotary shaft supported by the bearing, for example, when the set weight of the weight element is changed and the size of the bearing is varied corresponding to the set weight or when a space for interposing an elastic washer is provided between the unbalance weight and the bearing, the center of gravity of the weight element is not positioned on the line extending in a radial direction of the bearing and twisting will be produced in the rotary shaft. In other words, a first problem of this mounting structure is in that a space for an elastic washer cannot be provided or size (length) of the bearing cannot be freely set.
Since the unbalance weight is formed by fixing the weight element directly to the base portion (disc portion) as described above, during the rotational motion of the rotary shaft, lubricating oil of the bearing is scattered from a gap between the unbalance weight and the bearing towards a head cover and adheres to the head cover so as to damage it, and the lubricating oil leaks out of the head cover and the commercial value of the massage machine is deteriorated. This unfavorable state results in a second problem. In order to eliminate such an unfavorable state, oil-resistant material must be used as a raw material for the head cover and therefore the cost of the product is increased resulting in another disadvantage.
Additionally, the form of the vibration head is also an important factor to give variation to the massage action. Various massage machines of the vibration type have been proposed as hereinafter described where a plurality of kinds of massage action can be obtained by improving the shape of the vibration head:
(1) a massage machine where a convex curved surface and a concave curved surface are formed on outer circumferential portion of a vibration head corresponding to unevenness of a diseased part (Japanese utility model publication No. 53199/1977)
(2) a massage machine where the outer circumferential portion of a vibration head is formed as an ellipse having plural curved surfaces with different radii of curvature and thus, the degree of contact with a diseased part can be varied (Japanese utility model publication No. 4011/1981)
(3) a massage machine where three massage positions, i.e., circular arc surface, flat surface, square surface, are formed on an outer circumferential portion of a vibration head (Japanese utility model publication No. 4012/1981)
(4) a massage machine where a buffer cover for enclosing a buffer and a cover having hard projections are fixed on the outer circumferential portion of a vibration head and thus, soft massage and point massage can be obtained (Japanese utility model publication No. 42428/1982).
In addition to the above description, a massage machine where a vibrator attachment is detachably exchangeably installed to a vibration head (Japanese utility model application laid-open No. 93991/1978) has been proposed.
In each of the above-mentioned proposed items (1) through (4), a problem to be improved is in that only two or three massage positions can be obtained, in other words, various parts of the vibration head are not utilized as massage positions effectively to the maximum. Also in the proposal of installing the vibrator as attachment, a problem is in that the exchangeable and detachable installation is troublesome and the cost of the device becomes high.